Spectroscopic Properties of Two 5′-(4-Dimethylamino)Azobenzene Conjugated G-Quadruplex Forming Oligonucleotides

• Main Authors: Concetta Imperatore, Antonio Varriale, Elisa Rivieccio, Angela Pennacchio, Maria Staiano, Sabato D’Auria, Marcello Casertano, Carlo Altucci, Mohammadhassan Valadan, Manjot Singh, Marialuisa Menna, Michela Varra
• Format: Article
• Language: English
• Published: MDPI AG 2020-09-01
• Series: International Journal of Molecular Sciences
• Subjects: G-quadruplexes; conjugated aptamers; CD G-quadruplexes; fluorescence G-quadruplexes; azobenzenes; trans-cis conversion
• Online Access: https://www.mdpi.com/1422-0067/21/19/7103
• ISSN: 1661-6596; 1422-0067

The synthesis of two 5′-end (4-dimethylamino)azobenzene conjugated G-quadruplex forming aptamers, the thrombin binding aptamer (TBA) and the HIV-1 integrase aptamer (T30695), was performed. Their structural behavior was investigated by means of UV, CD, fluorescence spectroscopy, and gel electrophoresis techniques in K⁺-containing buffers and water-ethanol blends. Particularly, we observed that the presence of the 5′-(4-dimethylamino)azobenzene moiety leads TBA to form multimers instead of the typical monomolecular chair-like G-quadruplex and almost hampers T30695 G-quadruplex monomers to dimerize. Fluorescence studies evidenced that both the conjugated G-quadruplexes possess unique fluorescence features when excited at wavelengths corresponding to the UV absorption of the conjugated moiety. Furthermore, a preliminary investigation of the trans-cis conversion of the dye incorporated at the 5′-end of TBA and T30695 showed that, unlike the free dye, in K⁺-containing water-ethanol-triethylamine blend the trans-to-cis conversion was almost undetectable by means of a standard UV spectrophotometer.